An automatic coffee machine is known from European Patent No. EP 0 641 536 B1 corresponding to U.S. Pat. No. 5,471,910. The known automatic coffee machine includes a brewing unit including a brewing chamber being formed by a stationary tube section including a vertical axis and two locking elements, namely an upper locking element and a lower locking element. The upper locking element is connected to a rotary arm. The tube section is also called a brewing tube. An axial drive serves to move the rotary arm such that the upper locking element is introduced into the tube section and such that it leaves the tube section, respectively. A pivot drive serves to move the upper locking element into a parking position in which it is located outside of the axis of the tube section and into a stand-by position in which it is located in the axis of the tube section, respectively.
The axial drive and the pivot drive for the upper locking element are designed to be combined. The combined axial and pivot drive includes a worm transmission being located downstream of a motor and an axially movable and rotatable pivot column for moving the upper locking element (which is fixedly connected to the rotary arm) to reach a brewing position in which the locking element protrudes into the tube section. It also serves to move the upper stop element out off the tube section when moving the upper locking element into the parking position outside of the axis of the tube section and into the stand-by position in the axis of the tube section. The upper locking element is fixedly connected to the rotary arm to be commonly rotated therewith. One single motor serves to drive the combined axial and pivotal drive of the rotary arm with the upper locking element as well as a funnel and a pivoted coffee removing element. This motor is connected to the worm transmission and a dividing transmission located downstream thereof. The worm transmission is located on a spindle of the pivot column. The dividing transmission is located above the worm transmission, and it includes a guiding bush surrounding the pivot column, a channel bush surrounding the guiding bush, a bolt and a sliding block. The channel bush is arranged in the housing in a stationary manner, and it includes a bore for this purpose. The bolt engages the bore, the bolt being screwed into the housing in a radial direction from outside towards the inside. The bolt protrudes through the guiding bush in the region of a slot extending along a part of the circumference in a radial direction. In this way, the guiding bush cannot move in an axial direction while it may pivot with respect to the channel bush. The stationary channel bush includes a sliding path. The sliding path at its lower end includes a beginning portion being parallel to the axis. A thread-like increasing portion is located next to the beginning portion. The guiding bush also includes a sliding path which is parallel to the axis. The sliding block cooperates with the two sliding paths located in the channel bush and in the guiding bush. The sliding block is screwed into the pivot column. The known dividing transmission has a comparatively great number of components, and it is comparatively complicated and expensive.
The known automatic coffee machine includes a combined axial and pivot drive for the upper locking element and a separate vertical drive for the lower locking element. In this way, the two locking elements may be moved with respect to the tube section of the brewing chamber independent from one another to realize pressing, releasing and lifting of the tablet of coffee powder. There is no negative effect for the upper locking element during different phases of the brewing cycle. All stroke-like movements and pivotal movements of the upper locking element are derived from a combined drive by means of the dividing transmission. The specific movements may be determined in an exact and reproducible way. In this way, the control unit is relieved. Some movements are mechanically coupled by the dividing transmission. This does not only simplify the construction of the control unit, but it also increases operational safety in an advantageous way. The respective movements of the upper locking element and of the pivoted coffee removing element are derived from a drive, and they are coordinated with one another. Only a low number of sensors are required, and the mechanical forced coupling of the movements is advantageous. The stripping effect is coupled with the opening movement, meaning the pivotal movement from the stand-by position into the parking position. It is not necessary to realize and to drive a coffee charger. Due to the fact that the parking position is located outside of the axis of the brewing chamber, the brewing chamber is freely accessible from above. In this way, it is possible to arrange a unit for feeding coffee powder in a stationary way such that the coffee powder may be milled to be directly introduced into the brewing chamber. Due to the division of the movement of the upper locking element into an axial section between the brewing position and the stand-by position and a thread-like increasing section between the stand-by position and the parking position, it is possible to arrange up to three or more units for feeding coffee powder in a stationary way. In this way, it is possible to mill different kinds of coffee or different coffee bean preparations, as it is required for normal coffee, cappuccino, mocca and the like.
Furthermore, a vertical drive is connected to the lower locking element. The vertical drive includes another motor, a worm transmission located downstream of the motor and a spindle being guided in an axial direction. The spindle carries the lower locking element. In case the seal of the lower locking element of the brewing chamber shows a defect, there is the danger of a mixture of coffee and coffee powder entering the worm transmission and even the interior of the motor of the vertical drive. The worm transmission and the motor of the combined axial and pivotal drive may be damaged since the two worm drives and the two motors form a unit surrounded by a common housing.
Another automatic coffee machine is known from German Patent Application No. DE 41 33 697 A1 corresponding to U.S. Pat. No. 5,309,822. The upper locking element of the brewing unit is arranged at a rotary arm which is arranged to be pivoted about a stationary bearing. The upper locking element connected to the rotary arm can be pivoted from a stand-by position in the axis of the tube section above the brewing chamber into a parking position outside of the axis of the tube section. A pivot drive designed as an electric motor including a worm transmission located downstream thereof serves for this pivotal movement. An axial drive is also arranged on the rotary arm. The upper locking element can be moved into the tube section in a sealing way by the axial drive to reach the brewing position coming from the stand-by position. Furthermore, the known automatic coffee machine includes a vertical drive for the lower locking element. In this way, the known automatic coffee machine includes three drives for moving the two end pieces. Due to the arrangement of the rotary arm in a stationary bearing, it is possible to position and guide the upper locking element of the brewing chamber with the required exactness starting from the parking position to reach the stand-by position and the following brewing position without having to design the upper locking element as two parts. Furthermore, the known automatic coffee machine includes a pivoted coffee removing element for removing the tablet of coffee powder. The pivoted coffee removing element is connected to the rotary arm. Discharge of the used tablets of coffee powder is realized by pivotal movement of the rotary arm about its stationary bearing. The direction of the pivotal movement coincides with the direction of movement from the stand-by position into the parking position. Consequently, it is necessary to pivot the rotary arm back and forth twice during one brewing cycle. The first pivotal movement back and forth serves to realize brewing. The second movement back and forth serves to discharge the used tablet. The tablet has to be discharged in the parking position, and the upper locking element must not be located above the brewing chamber. The control unit of the automatic coffee machine has to take this into account.